This investigation is part of a multi-center study that will assess the safety of administering moderate and high doses of acamprosate and naltrexone both as single agents and in combination to non-treatment seeking alcohol dependant/abusing subjects. This study will also examine how single dose alcohol challenge influences the clinical tolerance of the drug doses and combinations that are to be tested. Finally, the pharmacokinetic interactions between acamprosate and naltrexone will be studied. Both behavioral and organ system toxicity will be evaluated in this study. Test agents will be administered to four groups of subjects in four phases following a mixed model random-block design. Placebo will be administered in Phase I, single agents in Phase II, while the final two phases will involve dose escalation of drug combinations. The data collected from this investigation will identify combinations of naltrexone and acamprosate that can be safely administered in a planned multi-center efficacy trial.